/Engine/Source/Runtime/Engine/Classes/Engine/NetConnection.h
Handles receiving NMT_Upgrade messages (including at stateless handshake level)
void HandleReceiveNetUpgrade ( uint32 RemoteNetworkVersion, EEngineNetworkRuntimeFeatures RemoteNetworkFeatures, [UE::Net::ENetUpgradeSource](API\Runtime\Engine\Engine\UE__Net__ENetUpgradeSource) NetUpgradeSource )